Isolated AST elevation due to macro-AST: A case report

Aspartate aminotransferase (AST) is a transaminase enzyme found in the liver, heart, skeletal muscle and various other tissues. A sustained isolated increase in AST levels, without accompanying clinical symptoms, liver disease, is uncommon and can be attributed to macro-AST mainly a benign high molecular weight complex. A 33-year-old female patient presented with symptoms of fatigue, body aches and mild abdominal discomfort. Her liver function tests indicated persistently elevated AST levels, which ranged from 412 to 730 U/L, while other liver enzymes and imaging results were unremarkable. Further investigations uncovered anaemia with haemoglobin levels between 5.9 and 9.3 g/dL, low levels of Vitamin D3 and absence of autoimmune or viral markers. A liver biopsy demonstrated normal histology. To assess the macro-AST, polyethylene glycol (PEG) precipitation was conducted and PEG AST level showed 171 U/L, thereby confirming the presence of macro-AST. The patient was clinically stable and showed no abnormal symptoms. In situations where there is isolated AST elevation without a clear cause, macro-AST should be considered. The PEG precipitation method serves as a straightforward and efficient diagnostic tool. Recognizing macro-AST can prevent unnecessary interventions and alleviate patient anxiety related to persistent abnormal test results.